Low-pressure discharge (e.g., fluorescent) lighting systems are widely employed illumination systems for general, energy-efficient use. The quality of object color under illumination by such system is an important aspect of the value of such light source. In general, the quality of object color has been described in terms of color rendering, which is a measure of the degree to which the psycho-physical colors of objects illuminated by a light source conform to those of a reference illuminant for specified conditions.
It has been generally known from basic research that a light source which has enhanced chroma (chromatic saturation) may serve to increase the visual clarity of illuminated objects, the feeling of contrast, and the brightness as perceived by viewers. It has also been generally known that people may have a preference for a slightly enhanced chroma of illuminated objects. However, it has heretofore been difficult to provide an enhanced (increased) chroma in an even or symmetrical manner. An asymmetrically increased chroma can lead to diminished color discrimination efficiency. Furthermore, if one were to employ some usual methods of maximizing color rendering (e.g., the Color Rendering Index, CRI), the result may be to penalize any change in color relative to the reference light source. Also, if one were to arbitrarily increase chroma to satisfy viewer preferences, it may result in a lamp having an insufficiently high CRI value to suit burgeoning global regulations.
Consumers have found that incandescent bulbs sold as REVEAL® by the General Electric Company to be quite appealing. One recent energy-efficient type of lamp provides fluorescent, solid-state diode, and fluorescent-solid state hybrid systems for providing the appealing color quality of REVEAL® incandescent bulbs. These have been described in patent publications, in e.g. United States Patent Publications 2009/0102348; 2009/0102391; 2009/0122530; and 2010/0096998, all of which are assigned to the same assignee as the present disclosure. However, these lamps may not always provide a balanced chroma increase.
It may be desirable to provide lamps having further improved color rendering properties, especially with respect to rendering of saturated colors.